Description:
------------
when using array_unique to unify an ArrayObject, PHP runs into a segfault.

Reproduce code:
---------------
<?php
$arrObj = new ArrayObject();
$arrObj->append('foo');
$arrObj->append('bar');
$arrObj->append('foo');

$arr = array_unique($arrObj);
?>

Expected result:
----------------
array (
  [0] => 'foo',
  [1] => 'bar'
)

or Error

Actual result:
--------------
Segfault